Automatic switch as used in telephone systems



March 7, 1939. R. N. SAXBY AUTOMATIC SWITCH AS USED IN TELEPHONE SYSTEMS Filed Dec. ll, 1956 Rose/w Mmm 5M5) Patented Mar. 7, 1939 PATENT QFFiQE I AUTOMATIC SWITCH AS USED IN TELEPHONE SYSTEMS Robert Norman Saxby, Liverpool, EnglancLassignor to Associated Telephone and Telegraph Company, Chicago, 111., a corporation of Delaware Application December 11, 1936,. Serial No. 115,326 In Great Britain January 13, 1936 4 Claims. (01. 175-306) The present invention relates to automatic switches as used in telephone systems and is more particularly concerned with the construction of contact banks for such switches. In the case of contact banks over which speech currents flow, it is desirable to provide screening means to minimise the electrostatic and inductive interaction between adjacent rows of contacts which is liable to give rise to cross-talk. It is accordingly common practice to make use of metal separators or spacers between the successive rows of contacts and to connect these spacers together electrically.

A method of commoning or connecting the bank separators already employed depends on the use of a bank assembly fixing bolt of slightly oval or other non-circular section in conjunction with similarly shaped holes in the spacers. During the tightening operation after assembly the bolt was given a half turn to cause it to bite into the soft metal separators and thus make an electrical connection with them. If however the bank is of the type secured together by countersunk screws so "as to reduce the overall height by eliminating the necessity for clearance for the bolt heads and fixing nuts, this arrangement is no longer practicable since the screws cannot be moved without altering the clamping effect. One possibility is to produce the same result by means of the fixing bolts clamping a plurality of banks to one another and to the mounting member. This arrangement is not altogether satisfactory in practice owing to the length of the fixing bolts and the considerable force required. An alternative arrangement is to make these bolts a driving fit but this does not give altogether reliable results. Moreover should a bank require to be removed during exchange maintenance the tight fitting bolts make this operation difiicult.

The object of the present invention is to provide an improved method of electrically commoning the metal separators between the rows of bank contacts whereby the bank assembling operation is not unduly complicated, removal of a bank is not hindered and a reliable electrical connectioning it into efiect reference being had to the accompanying drawing comprising Figs. 1-5.

Figs. 1 and 2 show a plan View and a front elevation respectively of a double contact bank assembly for a vertical and rotary switch, that is to say each level comprises two rows of contacts separated by an insulator. Fig. 3 illustrates a bank separator used in the assembly shown in Figs. 1 and 2. Fig. 4 shows an enlarged fragmentary view of a portion of Fig. 3. Fig. 5 is an enlarged illustration of an assembly detail of Figs. ,1 and 2. Switching connections to the speaking leads of a telephone system would ordinarily be made over a bank of the type shown in Figs. '1 and 2. In generaL'the effect of crosstalk due to bank contact assemblies is only likely to be appreciable if successive rows of contacts carry speech current i. e. in the case of a two-directional switch. The bank assembly is secured together by four screws H] which are countersunk in the upper fixing plate 9 and engage with threaded holes in the lower fixing plate H. The two holes H are provided to allow a number of banks to be clamped together by fixing bolts. Between each level of contacts indicated generally by l2 an aluminium separating plate or spacer I3 is interposed, having at one end' a substantially T-shaped slot I 4 the position of which will be appreciated better from the plan view of a separator, Fig. 3.

Fig. 4 shows an enlarged fragmentary view of the slot in the separator from which it will be seen that the slot is elongated to enable the strip I 5 to be inserted from the side without the necessity for threading it through the hole. Fig. 5 illustrates generally how the strip passes through the separators and around the insulators.

In the process of assembling the bank level by level, the strip of copper l5, one end of which has been previously secured to some part of the as- 40 sembly jig, is inserted into the slots l4. As each level is added the strip is repeatedly pulled tight in order to seat it firmly in the slots and to cause it to lie flush with the face of the bank. When the bank assembly is finally tightened up by the fixing screws l0, owing to the comparatively small area of contact l6 between the copper strip and the aluminium separators, the aluminium flattens under the pressure of the assembly of the bank with the result that the strip is locked in position and produces a good electrical connection. Moreover as a result of this deformation the overall dimensions of the bank assembly at this point do not vary from the overall dimensions at any other point. The strip is then clipped ofi at each end of the commoning and since the portion threaded through the slots will lie in close proximity to the face of the bank assembly it will take up no appreciable extra space but will nevertheless effect a good electrical connection between all the spacers in the bank.

I claim:

1. A bank contact structure for use in automatic switches comprising, in combination, a plurality of rows of contacts, supporting members of insulating material for the respective rows of contacts, shielding plates alternated with and extending between said rows of contacts, each of said plates having an opening adjacent one end thereof, means clamping said plates and supporting members together to provide a rigid as sembly, and a flexible conducting strip extending freely through the openings in each of said plates having contacting portions thereof clamped in engagement with said plates by said clamping means.

2. A bank contact structure for use in automatic switches comprising, in combination, a plurality of rows of contacts, supporting members of insulating material for the respective rows of contacts, shielding plates alternated with and extending between said rows of contacts, the ends of said plates being substantially flush with the ends of said supporting members and each thereof having an opening adjacent one end thereof, said openings being substantially in alignment, a flexible conducting strip extending through said openings and overlapping the ends of said supporting members, and means clamping said plates and supporting members together thereby to clamp said strip against said plates at spaced intervals along its length and to provide a rigid assembly.

3. A bank contact structure for use in automatic switches comprising, in combination, a plurality of rows of contacts, supporting members of insulating material for the respective rows of contacts, shielding plates alternated with and extending between said rows of contacts, each of said plates having an opening adjacent one end thereof, means clamping said plates and supporting members together to provide a rigid assembly, and a flexible conducting strip extending through the opening in each of said plates and including portions clamped in engagement with said plates, the opening in each of said plates including a narrowed channel portion extending to the edge of the plate, and said strip being of flattened cross section, whereby said strip may be inserted in said openings by way of the edges of the plates during assembly of the structure.

4. A bank contact structure for use in automatic switches comprising, in combination, a plurality of rows of contacts, supporting members of insulating material for the respective rows of contacts, shielding plates alternated with and extending between said rows of contacts, the ends of said plates being substantially flush with the ends of said supporting members and each thereof having an opening adjacent one end thereof, said openings being substantially in alignment, a flexible conducting strip extending through said openings and overlapping the ends of said supporting members, and means clamping said plates and supporting members together thereby to clamp said strip against said plates at spaced intervals along its length and to provide a rigid assembly, the opening in each of said plates including a narrowed channel portion extending to the edge of the plate, and said strip being of flattened cross section, whereby said strip may be inserted in said openings by way of the edges of the plates during assembly of the structure.

ROBERT NORMAN SAECBY. 

